The present invention relates generally to a cannula which may be used, in some embodiments, with a Ventricular Assist Device (“VAD”).
In certain disease states, the heart of a human or other mammalian subject lacks sufficient pumping capacity to meet the needs of the body. This inadequacy can be alleviated by providing a mechanical pump referred to as a Ventricular Assist Device (“VAD”) to supplement the pumping action of the heart. The intake of the VAD may be equipped with an intake cannula having an interior bore. The VAD and intake cannula may be positioned such that at least a portion of the intake cannula is positioned within a ventricle or atrium. This portion of the intake cannula, typically at or near an end of the cannula, includes an intake region where the interior bore of the cannula communicates with the surroundings. Thus, the VAD can take in blood from within the ventricle.
The discharge of a VAD may be connected to the interior bore of a discharge cannula. The discharge cannula has a discharge region, typically at or near an end of the cannula, where the interior bore of the cannula communicates with the surroundings. The discharge region is positioned in an artery or vein, most commonly in the aorta. Thus, the VAD can discharge blood through the discharge cannula into the artery or vein.
Other arrangements use cannulas with other blood pumping devices in a generally similar fashion. In general, the intake region of an intake cannula, or the discharge region of a discharge cannula, can be positioned within a portion of the circulatory system such as a vein, artery or coronary chamber.
The intake or discharge region of the cannula should resist movement caused by the flow of blood into or out of the cannula. This allows the cannula to remain stable and minimizes or prevents injury to the surrounding tissue, such as the wall or valve of the heart, or blood vessel. It is also desirable to minimize flow resistance through the cannula, and particularly the flow resistance of the intake or discharge region. Moreover, the flow pattern of the blood entering or leaving the cannula should minimize turbulence and eddying, which may destabilize the cannula as well as damage the flowing blood. Additionally, the intake or discharge region should be resistant to accidental blockage or suction which may occur if the intake or discharge region comes in contact with the heart or blood vessel wall. The intake or discharge region should be free of features such as sharp edges or projections which can damage the surrounding tissue. Also, the intake or discharge region should have a shape which can be formed readily. All of these factors, taken together, present a significant engineering challenge. Thus, there has been a need in the art for further improvement in cannula design.